Re: [PATCH 1/1] fsidd: require root credentials on abstract socket

[Steve Dickson <steved@redhat.com>]

On 9/6/26 9:13 PM, Olga Kornievskaia wrote:
> fsidd listens on an abstract UNIX domain socket which has no
> filesystem-level access control.  Any local unprivileged user can
> connect and issue mutating commands (get_or_create_fsidnum) that
> grow the reexport database without limit, degrading mountd
> performance.
> 
> Add a SO_PEERCRED check to reject connections from non-root
> clients.  The only legitimate client is mountd, which runs as root.
> 
> Fixes: 6fd2732d ("export: Add fsidd")
> Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
After all the recent fsidd changes this patch did
apply cleanly..

Committed... (tag: nfs-utils-2-9-3-rc4)

steved.
> ---
>   support/reexport/fsidd.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/support/reexport/fsidd.c b/support/reexport/fsidd.c
> index 9b80b451..c714386e 100644
> --- a/support/reexport/fsidd.c
> +++ b/support/reexport/fsidd.c
> @@ -7,6 +7,7 @@
>   #include <dlfcn.h>
>   #endif
>   #include <event2/event.h>
> +#include <sys/socket.h>
>   #include <sys/un.h>
>   #include <unistd.h>
>   
> @@ -147,6 +148,8 @@ static void srv_cb(evutil_socket_t fd, short ev, void *d)
>   {
>   	int cl = accept4(fd, NULL, NULL, SOCK_NONBLOCK);
>   	struct event *client_ev;
> +	struct ucred cred;
> +	socklen_t clen = sizeof(cred);
>   
>   	if (cl == -1) {
>   		if (errno == EMFILE || errno == ENFILE || errno == ENOMEM ||
> @@ -162,6 +165,12 @@ static void srv_cb(evutil_socket_t fd, short ev, void *d)
>   	(void)ev;
>   	(void)d;
>   
> +	if (getsockopt(cl, SOL_SOCKET, SO_PEERCRED, &cred, &clen) < 0 ||
> +	    cred.uid != 0) {
> +		close(cl);
> +		return;
> +	}
> +
>   	client_ev = event_new(evbase, cl, EV_READ | EV_PERSIST | EV_CLOSED, client_cb, event_self_cbarg());
>   	if (!client_ev || event_add(client_ev, NULL) == -1) {
>   		if (client_ev)